Advancements in communication technologies have permitted the development and deployment of mobile radio communication systems. Cellular, and cellular-like, communication systems are exemplary radio communication systems. The infrastructures of cellular, and other, communication systems have been widely deployed and regularly used by many. Successive generations of various types of communication systems have been developed and their operating parameters and protocols are promulgated in operating standards, promulgated by standard-setting bodies.
Various frequency allocations have been made by regulatory bodies for communications by way of radio communication systems operable pursuant to associated system standards. Mobile stations are typically utilized by users when communicating in a cellular, or other, mobile radio communication system. A mobile station is sometimes referred to as being a multi-mode mobile station when the mobile station is capable of operation by way of more than one type of mobile radio communication system. When a mobile station is positioned in an area encompassed by infrastructures of more than one mobile radio communication system with which the mobile station is operable, communications are carried out by way of a selected one of the communication systems. Selection is made, e.g., based upon a service subscription preference, user preference, or other criteria. And, when the mobile station is positioned at an area encompassed by the infrastructure of only one of the systems with which the mobile station is compatible, the mobile station communicates by way of the available system.
A multi-mode mobile station must include circuitry permitting its operation in each of the communication systems with which the mobile station is to communicate. Most simply, a mobile station is provided with multiple, independent circuitries of a number and type corresponding to the number and type of systems with which the mobile station is to operate. Sharing of common circuit portions is sometimes utilized to provide cost and size advantages.
Special challenges are presented with respect to antenna transducer elements when the different systems with which the mobile station is to operate utilize different frequencies. The antenna transducer elements must be operable at the different frequencies of operation of the different communication systems. The size required of an antenna transducer element is typically related to the frequencies of the signal energy that is to be transduced by the transducer element. Different antenna sizes are therefore generally required for the different systems with which the mobile station is to operate. The challenges become yet greater as the mobile stations must increasingly be packaged in smaller housings. Significant attention has been directed towards the development of an antenna transducer, operable over multiple frequency bands that is also of small dimension to permit its positioning within the housing of a compact-sized mobile station. A PIFA (Planar Inverted-F Antenna) is sometimes used in multi-mode mobile stations. A PIFA is of relatively compact size, exhibits a low profile, and provides for at least dual-band radiation. A PIFA, however, generally exhibits a narrow bandwidth. And, conventional efforts to enhance the bandwidth of a PIFA generally utilize a combination of the PIFA with a parasitic element. However, addition of a parasitic element increases the size of the resultant antenna structure. A need therefore exists for an improved, antenna structure of small dimensions that is also capable for use at multiple different frequencies.
It is in light of this background information related to antenna transducers for radio devices that the significant improvements of the present invention have evolved.